Light emitting device including light-transmissive member and lens member

ABSTRACT

A light emitting device includes: at least one semiconductor laser element; a base member on which the at least one semiconductor laser element is disposed; a light-transmissive member including: an upper surface, a lower surface, and a light-transmissive region through which laser light emitted from the at least one semiconductor laser element is transmitted from the lower surface to the upper surface; and a lens member through which the laser light emitted from the at least one semiconductor laser element, the lens member being fixed to the base member or the light-transmissive member. At least the light-transmissive region is made of sapphire. The light-transmissive member includes an incident surface on which the laser light is incident, the incident surface being an a-plane of the sapphire.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/790,090, filed on Feb. 13, 2020, which claims priority to JapanesePatent Application No. 2019-025353, filed on Feb. 15, 2019. The contentsof these applications are hereby incorporated by reference in theirentireties.

BACKGROUND 1. Technical Field

The present disclosure relates to a light emitting device and an opticaldevice including the light emitting device.

2. Description of Related Art

JP 2012-94728 A describes a semiconductor laser device in which asemiconductor laser element is hermetically sealed with a substrate anda cap, and a light-transmissive member disposed in a region where lightfrom the semiconductor laser element passes through.

There is also an optical device in which the polarization characteristicof light emitted from a light source is considered for utilization ofthe emitted light, such as a liquid crystal projector described in JP2019-3209 A.

SUMMARY

An object of the present disclosure is to obtain a light emitting devicewith a good polarization ratio.

A light emitting device according to one embodiment of the presentdisclosure includes: a semiconductor laser element; and alight-transmissive member including an upper surface, a lower surface,and a light-transmissive region through which laser light emitted fromthe semiconductor laser element is transmitted from the lower surface tothe upper surface. At least the light-transmissive region is made ofsapphire. The light-transmissive member includes an incident surface onwhich the laser light is incident, the incident surface being an a-planeof sapphire. The light-transmissive member is oriented so that apolarization direction of the laser light incident on the incidentsurface is parallel or perpendicular to the c-axis of sapphire in a topview.

A light emitting device according to one embodiment of the presentdisclosure includes: a semiconductor laser element; and alight-transmissive member including an upper surface, a lower surface, alight-transmissive region through which laser light emitted from thesemiconductor laser element is transmitted from the lower surface to theupper surface. At least the light-transmissive region is made ofsapphire. The laser light emitted from the semiconductor laser elementhas a far-field pattern of an oval shape. The light-transmissive memberincludes an incident surface on which the laser light is incident, theincident surface being an a-plane of sapphire. The light-transmissivemember is oriented so that a direction corresponding to a major-axisdirection of the oval shape of the laser light is parallel orperpendicular to the c-axis of sapphire in a top view.

An optical device according to one embodiment of the present disclosureincludes: the light emitting device according to one embodiment of thepresent disclosure; a polarizer element on which light emitted from thelight emitting device is incident; a liquid crystal panel on which lightemitted from the light emitting device and transmitted through thepolarizer element is incident; and a projection lens projecting aprojection image created according to light emitted from the lightemitting device.

The present disclosure implements a light emitting device with a goodpolarization ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a light emitting deviceaccording to an embodiment.

FIG. 2 is a schematic perspective view for describing the constituentsof the light emitting device according to the embodiment of FIG. 1 .

FIG. 3 is a schematic top view of the light emitting device according tothe embodiment of FIG. 1 .

FIG. 4 is a schematic top view for describing the constituents of thelight emitting device according to the embodiment of FIG. 1 .

FIG. 5 is a schematic cross-sectional view of the light emitting deviceaccording to the embodiment of FIG. 1 , taken along line V-V in FIG. 3 .

FIG. 6 is a schematic cross-sectional view showing the light emissionregion of the light emitting device according to the embodiment of FIG.1 , corresponding to the cross-sectional view of FIG. 5 .

FIG. 7 is a schematic top view showing the light emission region in thelight-transmissive member of the light emitting device according to theembodiment of FIG. 1 .

FIG. 8 is a schematic top view showing the light emission region in alens member of the light emitting device according to the embodiment ofFIG. 1 .

FIG. 9 shows experimental data obtained by measuring the polarizationratio while varying angles in a plane direction of thelight-transmissive member formed of sapphire.

FIG. 10 shows experimental data obtained by measuring the polarizationratio while varying angles in the plane direction of thelight-transmissive member formed of sapphire.

FIG. 11 shows experimental data obtained by measuring the polarizationratio while varying angles in the plane direction of thelight-transmissive member formed of sapphire.

FIG. 12 is a schematic diagram showing the experiment condition of FIGS.9 to 11 .

FIG. 13 shows experimental data obtained by measuring the polarizationratio while varying the angle in the height direction of thelight-transmissive member formed of sapphire.

FIG. 14 shows experimental data obtained by measuring the polarizationratio while varying the angle in the height direction of thelight-transmissive member formed of sapphire.

FIG. 15 shows experimental data obtained by measuring the polarizationratio while varying the angle in the height direction of thelight-transmissive member formed of sapphire.

FIG. 16 is a schematic diagram showing the experiment condition in FIGS.12 to 15 .

FIG. 17 shows experimental data obtained by measuring the polarizationratio while varying the thickness of the light-transmissive memberformed of sapphire.

FIG. 18 is a cross-sectional view of a light emitting device accordingto another embodiment.

FIG. 19 is a schematic diagram, of a liquid crystal projector equippedwith the light emitting device according to the embodiment of FIG. 18 .

DETAILED DESCRIPTION

In the description and the claims, the term “polygonal shape”encompasses polygonal shapes such as triangular shapes, quadrangularshapes, and the like with modified corners such as rounded corners,truncated corners, etc. The term “polygonal shape” also encompassespolygonal shapes with modification at intermediate portions of sides ofthe polygonal shapes (i.e., portions other than ends of sides of thepolygonal corners). That is, a polygonal shape with modification shouldbe construed as “a polygon” recited in the description and claims.

Similarly, other terms indicating specific shapes, such as a circle, arecess, a projection, etc., encompass respective shapes withmodification. This is similar for each side forming such a shape. Thatis, a side having ends with modification and/or an intermediate portionwith modification should be construed as “a side.” When indicating “apolygonal shape” or “a side” without intended modification separatelyfrom a modified “polygonal shape” or a modified “side”, such shapeswithout intended modification are referred to with the term “strict”,such as “a strict quadrangle.”

In the description and claims, when a plurality of elements correspondto a single constituent and are to be indicated separately from eachother, the term of such elements are referred to with the words “first,”“second,” etc. Such indication of elements with the words “first,”“second,” etc., for indicating the elements corresponding to a singleconstituent separately from each other may be different between thedescription and claims, when the elements to be indicated as “first,”“second,” etc., or the view of separation between “first,” “second,”etc., is different between the description and claims.

With reference to the drawings, certain embodiments of the presentinvention will be described below. Embodiments described below areintended to give a concrete form to the technical idea of the presentinvention, and are not intended to limit the scope of the presentinvention. In the description below, identical names and identicalreference numerals indicate identical or similar members, and repetitivedescription thereof may be omitted as appropriate. The size orpositional relationship of members in the drawings may be exaggeratedfor the sake of clarity.

Embodiments

FIG. 1 is a schematic perspective view of a light emitting device 1according to one embodiment. FIG. 2 is a schematic perspective view ofthe light emitting device 1 in which some components are not shown forthe purpose of showing the disposition of the constituents ofsemiconductor laser elements 20 in the light emitting device 1. In FIG.2 , a light-transmissive member 60 is indicated by broken lines to beshown in a transparent manner. FIG. 3 is a schematic top view of thelight emitting device 1. FIG. 4 is a schematic top view corresponding tothe perspective view of FIG. 2 . FIG. 5 is a schematic cross-sectionalview of the light emitting device 1 taken along line V-V in FIG. 3 .FIG. 6 is a schematic cross-sectional view showing an emission region oflight emitted from the semiconductor laser element 20, corresponding tothe cross-sectional view of FIG. 5 . In FIG. 6 , the components of thelight emitting device 1 hatched in FIG. 5 are not hatched, and insteadthe light emission region is hatched and represented by arrows. FIG. 7is a schematic top view showing the light emission region in a lensmember 70 of the light emitting device 1. FIG. 8 is a schematic top viewshowing the light emission region in the light-transmissive member 60 ofthe light emitting device 1. FIGS. 7 and 8 show the light emissionregions of the main portion of light as hatched regions defined by thebroken lines.

The light emitting device 1 includes a base member 10, foursemiconductor laser elements 20, four submounts 30, fourlight-reflective members 40, four protective elements 50, alight-transmissive member 60, and a lens member 70. An adhesive part 80formed of an adhesive agent is disposed between the light-transmissivemember 60 and the lens member 70.

The base member 10 has a quadrangular outer shape in a top view, anddefines a recess located inward of an outer periphery of the base member10. That is, the base member 10 includes a recess part that is recessedfrom an upper surface of the base member 10 toward a lower surface ofthe base member 10. The base member 10 includes the upper surface, anupward-facing surface, a lower surface, inner lateral surfaces, andouter lateral surfaces. In a top view, the upper surface forms a frame,and the recess is located inward of the frame. The base member 10includes stepwise portions 13 in the recess and, accordingly, includesstep upper surfaces and step lateral surfaces that form the stepwiseportions 13.

The upper surface intersects with the inner lateral surfaces and theouter lateral surfaces. The lower surface of the base member 10intersects with the outer lateral surfaces of the base member 10. In atop view, the inner lateral surfaces form a quadrangular shape. Theinner lateral surfaces consist of four lateral surfaces corresponding tothe sides of this quadrangular shape. The upward-facing surface forms anupper surface serving as the bottom of the recess, and is located higherthan the lowermost surface of the base member 10 and lower than theuppermost surface of the base member 10.

The stepwise portions 13 are located over the entire length of twoopposite lateral surfaces of four lateral surfaces that form the innerlateral surface. Other two lateral surfaces are not provided with thestepwise portions 13 excluding intersecting portions. As used herein, an“intersecting portion” refers to a portion where two lateral surfacesintersect with each other at respective corresponding ends of thelateral surfaces.

The two opposite lateral surfaces of the four lateral surfaces formingthe inner lateral surface are referred to as “first lateral surfaces14,” and the other two lateral surfaces of the four lateral surfaces arereferred to as “second lateral surfaces 15.” A direction parallel to thefirst lateral surfaces 14 in a top view is referred to as a “firstdirection X,” and a direction parallel to the second lateral surfaces 15in a top view is referred to as a “second direction Y” (see FIG. 4 ).The outer shape of the base member 10 in a top view is a quadrangularshape that is longer in the second direction Y than in the firstdirection X. Furthermore, in the light emitting device 1, the firstdirection X and the second direction Y are referred to as a “planedirection,” and a direction perpendicular to the first direction X andthe second direction Y is referred to as a “height direction.”

In each of regions where the stepwise portions 13 are formed, the steplateral surface intersects with the upward-facing surface, and the stepupper surface intersects with the inner lateral surface. In each ofregions where the stepwise portions 13 are not formed, the upward-facingsurface and the inner lateral surface intersects with each other. Theregion where the stepwise portion 13 are formed may have otherappropriate configurations. The stepwise portion 13 may be located at asingle lateral surface, or at three or more lateral surfaces.

The base member 10 includes a bottom part 12 including the upward-facingsurface, and a frame part 11 that includes the inner lateral surface andthe stepwise portions 13 and forms a frame surrounding the bottom part12 or the upward-facing surface. In the base member 10, the bottom part12 and the frame part 11 are joined to each other. The bottom part 12and the frame part 11 are made of different main materials. For example,in the base member 10, a ceramic may be used for a main material of theframe part 11, and a metal having a thermal conductivity higher than aceramic may be used for the main material of the bottom part 12.

Examples of such a ceramic include aluminum nitride, silicon nitride,aluminum oxide, and silicon carbide. Examples of such a metal includecopper, aluminum, iron, and alloy such as copper molybdenum, coppertungsten, and copper-diamond.

The base member 10 may not be formed of separate parts, such as thebottom part 12 and the frame part 11 separated from each other. Forexample, the base member 10 may be formed of a single member of which amain material is ceramic. For the base member 10, materials other than aceramic may be used; for example, a metal may be used.

The lower surface of the base member and the step upper surfaces 10 areprovided with respective metal films. The metal film on the lowersurface and the metal film on each step upper surface are connected toeach other via a metal passing inside the base member 10 and, therefore,can be electrically connected to each other. The metal films may beprovided in other regions in the base member 10. For example, the metalfilms may be disposed on the upward-facing surface instead of each stepupper surface, and on the upper surface or the outer lateral surfaces ofthe base member 10 instead of the lower surface of the base member 10.

The outer shape of each semiconductor laser element 20 has anelongated-rectangular shape in a top view. A lateral surfaceintersecting with one of two short sides of the elongated-rectangularshape functions as an emission end surface for light emitted from thesemiconductor laser element 20. Each of the upper surface and the lowersurface of each semiconductor laser element 20 has an area greater thanan area of the emission end surface.

Light (laser light) emitted from each semiconductor laser elementspreads to form an oval far-field pattern (hereinafter referred to as“the FFP”) in a plane parallel to the light emission end surface. TheFFP is a shape and intensity distribution of emitted light at a positionspaced apart from the emission end surface. In the light intensitydistribution, a portion of emitted light having an intensity is 1/e² ormore with respect to the peak light intensity is referred to as a“main-portion light”

The FFP of light emitted from each semiconductor laser element 20 has anoval shape, which is shorter in a layer direction along each of aplurality of semiconductor layers including an active layer than in alayered direction, in which the plurality of semiconductor layers arelayered, perpendicular to the layer direction. The layer direction (theminor-axis direction of the oval shape) may be referred to as a“parallel direction of the FFP,” and the layered direction (themajor-axis direction of the oval shape) may be referred to as a“perpendicular direction of the FFP.”

As used herein, according to the light intensity distribution of theFFP, an angle corresponding to the full width at half maximum in thelight intensity distribution is referred to as a “divergence” of lightemitted from the semiconductor laser element. A divergence of light inthe perpendicular direction of the FFP is referred to as a “divergencein the perpendicular direction,” and a divergence of light in a paralleldirection of the FFP is referred to as a “divergence in the paralleldirection.”

For the semiconductor laser elements 20, a semiconductor laser elementsconfigured to emit blue light can be employed. Alternatively,semiconductor laser elements configured to emit green light or redlight, or light of other colors may be employed.

As used herein, the term “blue light” refers to light having peakemission wavelength in a range of 420 nm to 494 nm. The term “greenlight” as used herein refers to light having a peak emission wavelengthin a range of 495 nm to 570 nm. The term “red light” as used hereinrefers to light having a peak emission wavelength in a range of 605 nmto 750 nm. Examples of the semiconductor laser elements configured toemit blue light include semiconductor laser elements containing anitride semiconductor. Examples of the nitride semiconductor includeGaN, InGaN, and AlGaN.

Each submount 30 has a flat rectangular prism-shape, and includes anupper surface, a lower surface, and lateral surfaces. Of lengths of eachsubmount 30, a length in the top-bottom direction is the smallest. Eachsubmount 30 may have any appropriate shape other than a rectangularprism. The submounts 30 are formed of, for example, silicon nitride,aluminum nitride, or silicon carbide. Any other appropriate material maybe employed for the submounts 30.

Each light-reflective member 40 includes a light-reflective surface thatreflects light. The light-reflective surface is inclined relative to alower surface of the light-reflective member 40. That is, thelight-reflective surface is not perpendicular or parallel to the lowersurface of light-reflective member 40. For example, the light-reflectivesurface may be a flat surface (an inclined surface) at an inclinationangle of 45 degrees relative to the lower surface of thelight-reflective member 40. The light-reflective surface may be a curvedsurface.

For a main material of the light-reflective members 40 that forms theouter shape of the light-reflective members 40, a glass, a metal, etc.,can be employed. The main material of the light-reflective members 40 ispreferably heat resistant, and for example, quartz or glass such as BK7(borosilicate glass), a metal such as aluminum, or Si can be used.

The light-reflective surface may have a light reflectance of 99% or morefor the peak wavelength of laser light to be reflected. For such alight-reflective surface, a metal such as Ag or Al, or a multilayerdielectric film of Ta₂O₅/SiO₂, TiO₂/SiO₂, Nb₂O₅/SiO₂ or the like may beused. A light reflectance of the light-reflective surface is equal to orless than 100%.

The protective elements 50 serve to prevent breakdown of specificelements (for example, the semiconductor laser elements 20). Examples ofthe protective elements 50 include Zener diodes for which Si is used.

The light-transmissive member 60 has a flat rectangular prism-shape, andincludes an upper surface, a lower surface, and lateral surfaces. Oflengths of the light-transmissive member 60, a length in the top-bottomdirection is smallest. As used herein, the expression “lighttransmissive” refers to having a light transmittance of 80% or more. Thelight-transmissive member 60 may have any appropriate shape other than arectangular prism-shape. The light-transmissive member 60 may partiallyinclude a region that is not light-transmissive.

Sapphire is used for a main material of the light-transmissive member60. The light-transmissive portion in the light-transmissive member 60is made of sapphire. Sapphire has a relatively high refractive index andalso has a relatively high strength. The light-transmissive member 60 ismade of an undoped material.

The lower surface or the upper surface of the light-transmissive member60 is a plane parallel to the c-axis in the plane orientation ofsapphire. More specifically, the lower surface or the upper surface ofthe light-transmissive member 60 is the a-plane, or may be the m-plane.Alternatively, the lower surface or the upper surface of thelight-transmissive member 60 is the c-plane in the plane orientation ofsapphire.

The width (thickness) of the light-transmissive member 60 between anupper surface and a lower surface of the light-transmissive member 60may be in a range of 0.2 mm to 1.0 mm, preferably 0.3 mm to 0.6 mm. Thearea of the upper surface of the lower surface may be in the range of2.0 mm² to 100 mm², preferably 9.0 mm² to 50 mm². Such dimension allowsfor contributing to downsizing of the light emitting device 1 whilemaintaining sufficient strength of the light emitting device 1. Thelight-transmissive member 60 may have any appropriate dimensions otherthan this range.

The adhesive part 80 is obtained by curing an adhesive agent. For theadhesive agent forming the adhesive part 80, UV-curing resin can beused. UV-curing resin is cured within relatively short time without thenecessity of heating.

The lens member 70 has a shape in which lenses are disposed on a flatupper surface, and includes an upper surface, a lower surface, andlateral surfaces. Accordingly, while the lower surface of the lensmember 70 is a flat surface, the upper surface of the lens member 70includes a planar region 71 intersecting with the lateral surfaces ofthe lens member 70 and being parallel to the lower surface of the lensmember 70, and a lens region 72 forming lens surfaces. The lens region72 is surrounded by the planar region 71, and the lens shape is formedat a location higher than the flat surface.

The lens region 72 includes a shape in which a plurality of lenses areconnected in a single direction. More specifically, four lenses areconnected in a single lateral surface direction in a top view. In thelens member 70, in a top view, a length in the single lateral surfacedirection (the connecting direction P) is greater than a lengthperpendicular to the length in the single lateral surface direction (seeFIG. 3 ). In a top view, the length in the direction of a line crossingall the four lenses is greater than the length in the direction of aline perpendicular the line crossing all the four lenses.

Further, in the planar region 71, a width W1, which is a shortestdistance (width) between a position on the planar region 71 intersectingwith the lateral surface and the lens region 72 in the connectingdirection P, is greater than width W2, which is a shortest distance(width) between a position on the planar region 71 intersecting with thelateral surface and the lens region 72 in a direction perpendicular tothe connecting direction P (see FIG. 3 ). In view of downsizing thelight emitting device 1, preferably this relationship is establishedwith at least one of two lateral surfaces parallel to the connectingdirection P. The lens member 70 may be formed of glass such as BK7, forexample.

Next, the light emitting device 1 including components as describedabove will be described. The semiconductor laser elements 20 and theprotective elements 50 are mounted on the submounts 30. A singlesemiconductor laser element 20 and a single protective element 50 aredisposed on each of the submounts 30. Accordingly, four submounts 30 areprovided for four semiconductor laser elements 20.

A plurality of semiconductor laser elements 20 or a plurality ofprotective elements 50 may be disposed on a single submount 30. Eachprotective element 50 may be disposed at a position other than thesubmounts 30. The light emitting device 1 may not include the protectiveelements 50.

A metal film is disposed on the upper surface of each submount 30. Acorresponding semiconductor laser element 20 and a correspondingprotective element 50 are disposed on and bonded to the metal film. Thelower surface of the semiconductor laser element 20 is bonded to themetal film at a predetermined position such that the emission endsurface of the semiconductor laser element 20 aligns with or is locatedoutward of a corresponding lateral surface of the submount 30. Such adisposition allows for inhibiting light emitted from the semiconductorlaser element 20 from being incident on the upper surface of thesubmount 30.

Note that, when the emission end surface of the semiconductor laserelement 20 is located outward of a corresponding lateral surface of thesubmount 30, an excessively great distance between the emission endsurface of the semiconductor laser element 20 and the correspondinglateral surface of the submount 30 may cause the bonding unstable, andaccordingly the emission end surface of the semiconductor laser element20 and the corresponding lateral surface of the submount 30 may bespaced apart from each other at a slight distance. For example, thedistance between the emission end surface of the semiconductor laserelement 20 and the corresponding lateral surface of the submount 30 ispreferably 0.05 mm or less. The semiconductor laser element 20 may bedisposed such that the emission end surface of the semiconductor laserelement 20 is located inward of a corresponding lateral surface of thesubmount 30, at a position where the light is not incident on the uppersurface of the submount 30.

The submount 30 can function to release heat generated at thesemiconductor laser element 20. More specifically, the submount 30 isformed with a material having a thermal conductivity higher than that ofthe semiconductor laser element 20. Accordingly, when the submount 30has this heat-releasing function, the submount 30 can be regarded as aheat dissipating member.

In view of heat dissipation property, the submount 30 preferably has athermal conductivity higher than a thermal conductivity of theupward-facing surface of the base member 10. For example, when theupward-facing surface of the base member 10 is made of aluminum nitride,silicon carbide is preferably used for the submount 30.

Each submount 30 can be used to adjust the emission position of lightfrom a corresponding semiconductor laser element 20. When determiningthe emission position of light according to the disposition position ofother components, a thickness of each submount 30 is set to apredetermined value, and a corresponding semiconductor laser element 20is disposed on the submount 30. For example, in the light emittingdevice 1, the emission position is determined according to thepositional relationship with the light-reflective members 40. When thesubmounts 30 are used to adjust the emission position of light from thesemiconductor laser element 20 the submounts 30 can be regardedadjustment members.

Next, the submounts 30 are disposed on the upward-facing surface of thebase member 10. That is, the semiconductor laser elements 20 or theprotective elements 50 are disposed on the upward-facing surface side ofthe base member 10. The four submounts 30 are disposed such that theemission end surfaces of respective corresponding semiconductor laserelements 20 are in the same plane. The emission end surfaces may not bein the same plane, and disposition positions of the submounts 30 mayindividually adjusted.

The four submounts 30 are arranged between opposite first lateralsurfaces 14 or opposite stepwise portions 13. The four submounts 30 arearranged in the second direction Y. Light emitted from the disposedsemiconductor laser elements 20 propagates toward one of opposite secondlateral surfaces 15, or in the first direction X.

The FFP's of light emitted from the four semiconductor laser elements 20are identical to one another in the perpendicular direction and theparallel direction. As used herein, the expression “identical” permits adifference of 3 degrees or less. Light emitted from each semiconductorlaser element 20 and propagating along the optical axis advances in thefirst direction X. A portion of light forming the major axis of the ovalFFP is projected on a line perpendicular to the upward-facing surface. Aportion of light forming the minor axis of the FFP is projected on aline in the second direction Y.

The direction of the line on which the light forming the major axis ofthe FFP is projected is referred to as a “direction M corresponding tothe perpendicular direction of the FFP,” and the direction of the lineon which the light forming the minor axis of the FFP is projected isreferred to as a “direction N corresponding to the parallel direction ofthe FFP.”

Accordingly, the perpendicular direction of the FFP of light emittedfrom the semiconductor laser element 20 corresponds to the directionperpendicular to the upward-facing surface, and the parallel directionof the FFP of light emitted from the semiconductor laser element 20corresponds to the second direction Y.

Next, the light-reflective members 40 are disposed on the upward-facingsurface of the base member 10. A single light-reflective member 40 isdisposed for each submount 30 or for each semiconductor laser element20. A single light-reflective member 40 may be disposed for a pluralityof submounts 30 or a plurality of semiconductor laser elements 20.

Each light-reflective member 40 is disposed so that the main-portionlight emitted from a corresponding semiconductor laser element 20 isincident on the light-reflective surface. Accordingly, eachlight-reflective member 40 is located at a position in the propagationdirection of light emitted from the corresponding semiconductor laserelement 20, and provided with the light-reflective surface. The fourlight-reflective members 40 are disposed such that their respectivelight-reflective surfaces are aligned in the same plane. Thelight-reflective surfaces may not necessarily be aligned in the sameplane.

The four light-reflective members 40 are arranged between opposite firstlateral surfaces 14 or opposite stepwise portions 13. The fourlight-reflective members 40 are arranged in the second direction Y. Eachof the four light-reflective members 40 is disposed between a respectiveone of the semiconductor laser elements 20 and the second lateralsurface 15 toward which light emitted from the semiconductor laserelements 20 is to be propagated.

The light-reflective members 40 are disposed to be spaced apart from thesubmounts 30 or the semiconductor laser elements 20 at a predetermineddistance. Accordingly, when regarding a single semiconductor laserelement 20 and a single light-reflective member 40 on which main-portionlight emitted from the single semiconductor laser element 20 is incidentas a single light emitting unit, a distance between a correspondingsubmount 30 and a corresponding light-reflective member 40 or a distancebetween a corresponding semiconductor laser element 20 and acorresponding light-reflective member 40 is uniform among the four lightemitting units.

In the light emitting device 1, light propagating along the optical axispropagates in the direction parallel to the upper surface of acorresponding submount 30, reflected by the light-reflective surface,and propagates upward perpendicularly to the upward-facing surface. Asshown in FIG. 7 , reflection by the light-reflective surface causes thedirection M corresponding to the perpendicular direction of the FFP tobe changed from the direction perpendicular to the upward-facing surfaceto the first direction X. The reflection by the light-reflective surfacedoes not cause change of the direction N corresponding to the paralleldirection of the FFP, and the direction N remains to be the seconddirection Y.

Next, in order to electrically connect the semiconductor laser elements20 and the protective elements 50, wirings are bonded. By the wirings,the semiconductor laser elements 20 and the protective elements 50 areelectrically connected to the metal films disposed on the step uppersurfaces. Accordingly, the semiconductor laser elements 20 and theprotective elements 50 are supplied with power from an external powersupply via the metal film disposed on the lower surface of the basemember 10.

Next, the light-transmissive member 60 is disposed on the upper surfaceof the base member 10. The lower surface of the light-transmissivemember 60 and the upper surface of the base member 10 are bonded to eachother. A metal film for bonding with the base member 10 is disposed inthe vicinity of the outer edge of the lower surface of thelight-transmissive member 60.

With this metal film, the light-transmissive member 60 is secured to thebase member 10 via Au—Sn or the like.

The light-transmissive member 60 is has a size such that an outerperiphery of the light-transmissive member 60 located in the vicinity ofthe outer lateral surfaces of the base member 10 in a top view. Morespecifically, for example, the light-transmissive member 60 has a sizesuch that the light-transmissive member 60 overlaps 70% or more of alength between the outer lateral surface and the inner lateral surfacein the upper surface of the base member 10. This allows for increasing abonding area with the upper surface of the base member 10. Furthermore,as will be described below, this also allows for increasing a bondingarea with the lens member 70.

Light emitted from each semiconductor laser element 20 and reflected bythe light-reflective surface of a corresponding light-reflective member40 is incident on the lower surface of the light-transmissive member 60while spreading. That is, the lower surface of the light-transmissivemember 60 can be regarded as the light incident surface. Lightpropagating along the optical axis is perpendicularly incident on thelower surface of the light-transmissive member 60.

In the lower surface or the upper surface of the light-transmissivemember 60, the direction M corresponding to the perpendicular directionof the FFP is the first direction X, and the direction N correspondingto the parallel direction of the FFP is the second direction Y. 80% ormore of the incident light is transmitted to be emitted from the uppersurface of the light-transmissive member 60. That is, a region of thelight-transmissive member 60 through which light passes islight-transmissive.

Bonding the light-transmissive member 60 to the base member 10 forms aclosed space where the semiconductor laser elements 20 are disposed.When open space, such as a recess, is closed to be a closed space, thelight-transmissive member 60 can be regarded as a cover.

The closed space where the semiconductor laser elements 20 are disposedis hermetically sealed. Hermetic sealing allows for inhibitingattraction of organic substances or the like to the light emission endsurfaces of the semiconductor laser elements 20.

Next, the lens member 70 is disposed above the light-transmissive member60, and is secured to the light-transmissive member 60. The lens member70 is adjusted and secured to a position that allows light emitted fromthe light-transmissive member 60 to be properly controlled by thelenses. An adhesive agent is applied between the lens member 70 disposedat the position where it is to be fixed and the light-transmissivemember 60. The lens member 70 is secured by the adhesive agent, and theadhesive agent is cured to obtain the adhesive part 80.

The lens member 70 is disposed so that one of the connected lensescontrols light from a corresponding semiconductor laser element 20.Accordingly, the connected four lenses is configured to controlrespective light beams from the four semiconductor laser elements 20.

More Specifically, in the light emitting device 1, light transmittedthrough the lenses of the lens member 70 is collimated and emitted fromthe lens member 70. That is, the lens member 70 includes collimatinglenses. With the collimating lenses, light not collimated when incidenton the light-transmissive member 60 is transmitted through thelight-transmissive member 60 while spreading, and is transmitted throughthe lens member 70, to be a collimated light and emitted. Note that,configurations other than collimating may be employed for control oflight, and condensing or diffusing may be employed.

The lens member 70 is disposed such that the lens connecting direction Pand the alignment direction of the semiconductor laser elements 20 (thesecond direction Y) agree with each other in a top view. The lens member70 is disposed such that the lens connecting direction P and thedirection N corresponding to the parallel direction of the FFP andincident on the lens member 70 agree with each other, and the directionperpendicular to the connecting direction P (the first direction X) in atop view and the direction M corresponding to the perpendiculardirection of the FFP incident on the lens member 70 agree with eachother.

The lens member 70 is disposed so that light emitted from eachsemiconductor laser element 20 propagating along the optical axis istransmitted through the apex of corresponding lens (a portion of thelens at the highest position in the top-bottom direction of the lens).In a top view, the lens region 7 has two opposite ends including a firstend and a second end in the width in the first direction X, such thatthe first end is located at the upper surface of the base member 10, andthe second end is located inward of the inner lateral surfaces (insidethe recess in a top view). In order to control a greater amount of lightand to downsize the light emitting device 1, the first end is locatedabove the upper surface of the base member 10.

On the other hand, in connection with the lens member 70, two oppositeends in the width of the lens region 72 in the second direction Y arenot located at the upper surface of the base member 10 in a top view,but are located inward of the inner lateral surfaces. That is, the lensmember 70 is disposed such that the lens region 72 is positioned betweenthe opposite first lateral surfaces 14 in a top view. With the stepwiseportions 13 located at the first lateral surfaces 14, the lens region 72can be located inward of the first lateral surfaces 14.

In a top view, the region where the adhesive agent is provided (theregion where the adhesive part 80 is disposed) overlaps with the planarregion 71 of the lens member 70 and does not overlap with the lensregion 72. Accordingly, the adhesive agent is disposed in the vicinityof the outer edge of the lower surface of the lens member 70. Theadhesive agent is provided in the vicinity of the sides extending in thefirst direction X, of four sides of the lower surface of the lens member70.

In the planar region 71 of the lens member 70, the width W1 in theconnecting direction P is greater than the width W2 in the directionperpendicular to the connecting direction P. This allows for increasingthe bonding area with the light-transmissive member 60. In such amanner, the light emitting device 1 is manufactured.

Experimental data on the relationship between the plane orientation ofsapphire or the light incident direction and the polarization ratio oflight will be described below.

FIGS. 9 to 11 show experimental data obtained by measuring thepolarization ratio with the light-transmissive member 60 made ofsapphire, while varying angles in the plane directions for each of thecase in which the incident plane is the a-plane and the case in which itis the c-plane. FIG. 9 shows the experimental data where TE-modesemiconductor laser elements emitting blue light are used for thesemiconductor laser elements 20. FIG. 10 shows the experimental datawhere TE-mode semiconductor laser elements emitting green light are usedfor the semiconductor laser elements 20. FIG. 11 shows the experimentaldata where TM-mode semiconductor laser elements emitting red light areused for the semiconductor laser elements 20. FIG. 12 is a schematicdiagram showing the experiment condition under which the experimentaldata shown in FIGS. 9 to 11 is obtained.

As shown in FIG. 12 , in this experiment, measurement was performed in astate in which light propagating along the optical axis of light emittedfrom the semiconductor laser element 20 is perpendicularly incident onthe incident surface of the light-transmissive member 60. Furthermore,measurement was performed at various angles with the light-transmissivemember 60 rotated about the optical axis while maintaining theperpendicular incident state. In the description below, this angle isreferred to as a “plane rotation angle α.”

In the case in which the incident surface is the a-plane, the planerotation angle α where the direction corresponding to the perpendiculardirection of the FFP and the c-axis of sapphire are parallel to eachother was defined as 0 degrees, and the plane rotation angle α where thedirection corresponding to the perpendicular direction of the FFP andthe c-axis of sapphire are perpendicular to each other was defined as 90degrees. FIG. 8 shows the values of the plane rotation angles α wherethe incident surface of the light-transmissive member 60 of the lightemitting device 1 is the a-plane of sapphire and the c-axis is orientedas indicated by the arrow in FIG. 8 .

In the case in which the incident surface is the c-plane, the planerotation angle α where the direction corresponding to the perpendiculardirection of the FFP and the a-axis of sapphire are parallel to eachother was defined as 0 degrees, and the plane rotation angle α where thedirection corresponding to the perpendicular direction of the FFP andthe a-axis of sapphire are perpendicular (parallel to the m-axis) wasdefined as 90 degrees.

Both the light-transmissive member 60 with an incident surface of thea-plane and the light-transmissive member 60 with an incident surface ofthe c-plane had a thickness of 500 μm. The polarization ratio measuredwithout the light-transmissive member 60 was 3134 TE/TM for blue light,2487 TE/TM for green light, and 36 TM/TE for red light. For comparisonpurposes, in FIGS. 9 to 11 , the polarization ratio without thelight-transmissive member is indicated by the solid line.

In measurement, Glan-Laser calcite polarizer available from Thorlabs,Inc. was used as a polarizer E2, a metal film ND filter available fromMelles Griot K. K. was used as a ND filter E3, and a detector photodiodeavailable from Hamamatsu Photonics K. K. was used as a detectorphotodiode E4.

According to the measurement results in FIGS. 9 to 11 , it can beunderstood that, when the incident surface is the c-plane, thepolarization ratio does not greatly change in response to a change inthe angle. That is, it is considered that the c-plane has no or verysmall dependence of polarization ratio on rotation of the planedirection.

On the other hand, when the incident surface is the a-plane, thepolarization ratio changes in response to a change in the plane rotationangle α. It can be understood that the polarization ratio is reducedwhen the plane rotation angle α increases from 0 degrees to 45 degrees,and increases when the plane rotation angle α increases from 45 degreesto 90 degrees. Also, it can be understood that the polarization ratio isthe greatest at 0 degrees or 90 degrees, and is the lowest at 45degrees.

When the plane rotation angle α is 45 degrees, the polarization ratio isgreatly reduced. As shown in each of FIGS. 9 to 11 , a polarizationratio was not good when the plane rotation angle α was in a range of 30degrees to 60 degrees, and the value of polarization ratio was in arange of 1 to 5.

On the other hand, the high polarization ratio was obtained when theplane rotation angle α is 0 degrees and 90 degrees. That is, it isconsidered that a good polarization ratio is obtained when the planerotation angle α is 0 degrees or 90 degrees, for both of TE-mode lightand TM-mode light. Accordingly, it is considered that even a lightemitting device including both TE-mode and TM-mode semiconductor laserelements can have a good polarization ratio.

Furthermore, it is considered that a good polarization ratio is obtainedalso with a light emitting device in which the direction correspondingto the perpendicular direction of the FFP and the directioncorresponding to the parallel direction of the FFP in the incidentsurface are different from each other by 90 degrees in a top view. Forexample, it is considered that a good polarization ratio is obtainedalso with the light emitting device 1 in which two semiconductor laserelements 20 are disposed so that light emitted from the twosemiconductor laser elements propagate along respective optical axes indirections different from each other by 90 degrees in a top view, andthe light-reflective members 40 are disposed so as to respectively causethe light propagating along the optical axes to advance perpendicularlyupward.

As shown in FIG. 11 , light with a low polarization ratio value (lightwith polarization ratio value of a two-digit number) before transmittedthrough the light-transmissive member 60 has the polarization ratiovalue higher after transmitted through the light-transmissive member 60with a plane rotation angle α of 0 degrees or 90 degrees than beforetransmitted through the light-transmissive member 60. From FIGS. 9 and10 , it can be understood that, light having a high polarization ratiovalue (the light with polarization ratio value of a four-digit value)before transmitted through the light-transmissive member 60 has thepolarization ratio value substantially the same or lower aftertransmitted through the light-transmissive member 60 with a planerotation angle α of 0 degrees or 90 degrees than before transmittedthrough the light-transmissive member 60.

With reference to FIGS. 9 and 10 , the polarization ratio that was 2000or more with a plane rotation angle α of 0 degrees was reduced to about200 with a plane rotation angle α of 5 degrees, and was reduced to about50 with a plane rotation angle α of 10 degrees. With reference to FIG.11 , with a plane rotation angle α of 10 degrees, the polarization ratiovalue was lower than the value of light before transmitted through thelight-transmissive member 60.

These result shows high dependence of the polarization ratio on theplane rotation angle α when the a-plane is the incident surface.Furthermore, it is considered that, in order to obtain a goodpolarization ratio, the plane rotation angle α is preferably in a rangeof 0 degrees to 10 degrees, or a range of 80 degrees to 90 degrees. Thisis similar in the case in which a plane rotation angle α is in a rangeof 90 degrees to 180 degrees, 180 degrees to 270 degrees, 270 degrees to360 degrees.

The maximum value of the polarization ratio in the a-plane than that inthe c-plane. That is, with a plane rotation angle α of 0 degrees or 90degrees, a polarization ratio can be higher in the a-plane than in thec-plane.

FIGS. 13 to 15 show experimental data obtained by measuring thepolarization ratio with the light-transmissive member 60 made ofsapphire, while varying the light incident angles on the incidentsurface for each of the case in which the incident surface is thea-plane and the incident surface is the c-plane. In the descriptionbelow, this incident angle is referred to as a “plane inclination angleβ.” FIG. 13 shows experimental data with a plane rotation angle α of 0degrees.

FIG. 14 shows experimental data with a plane rotation angle α of 45degrees. FIG. 15 shows experimental data with a plane rotation angle αof 90 degrees. FIG. 16 is a schematic diagram showing the experimentcondition under which the experimental data shown in FIGS. 13 to 15 isobtained.

As shown in FIG. 16 , this experiment is different from the experimentshown in FIG. 12 , in which spreading light of FFP is allowed to beincident on the light-transmissive member 60. In this experiment, lightpropagating along the optical axis of light emitted from thesemiconductor laser element 20 is collimated by a collimating lens E1and narrowed by a diaphragm E5 before incident on the light-transmissivemember 60.

The expression “a plane inclination angle β of 0 degrees in the graphsof FIGS. 13 to 15 ” indicates the state where light propagating alongthe optical axis is perpendicularly incident on the incident surface.That is, the disposition of the light-transmissive member 60 in thelight emitting device 1 corresponds to the state of 0 degrees.Therefore, when the plane inclination angle β is 90 degrees, light isnot incident on the lower surface of the light-transmissive member 60but is incident on a lateral surface of the light-transmissive member60. FIG. 18 shows the case in which the light-transmissive member 60 isdisposed to be inclined (where the plane inclination angle β is0°<β<90°).

The thickness of the light-transmissive member 60 and the polarizer E2,the ND filter E3, and the detector photodiode E4 that are employed aresimilar to those shown in FIG. 12 . FIGS. 13 to 15 show the measurementresult using a semiconductor laser element emitting blue light as thesemiconductor laser element 20, similarly to the measurement shown inFIG. 9 .

From the measurement result shown in FIGS. 13 to 15 , it can beunderstood that change in the polarization ratio in response to a changein degrees is greater in the c-plane than in the a-plane. Also, it canbe understood that change in polarization ratio in response to a changein degrees is small in the a-plane. That is, the polarization ratio isnot dependent or less dependent on the plane inclination angle β in thea-plane.

Neither the a-plane nor the c-plane show a significant change in apolarization ratio according to the angle of the plane inclination angle(3, such as reduction of a polarization ratio of 1000 or more to a two-or one-digit value.

With reference to FIGS. 13 and 15 , The greater the planar inclinationangle β is, the closer the polarization ratio value in the c-plane tothe polarization ratio value in the a-plane. According to this result,it is considered that the characteristic of the polarization ratio isnot greatly varied in a plane parallel to the c-axis.

That is, a plane rotated at the plane inclination angle β by 90 degreesfrom the c-plane is a plane parallel to the c-axis, and the directioncorresponding to the perpendicular direction of the FFP and the c-axisof sapphire are parallel to each other. The a-plane is also parallel tothe c-axis, and with a plane rotation angle α of 90 degrees (FIG. 15 ),the a-plane is parallel to the c-axis irrespective of the planeinclination angle β (for example, a plane inclined by 90 degrees is them-plane). Accordingly, it is considered that a plane parallel to thec-axis allows for obtaining a measurement result similar to that in thea-plane.

Comparing with FIG. 9 , it can be understood that, in the c-plane, thecollimating caused great increase of the polarization ratio. That is,when light is transmitted through the c-plane, the collimation oftransmitted light (degree of collimation of the collimated light)greatly influences the polarization ratio. On the other hand, in thea-plane, the polarization ratio is not greatly varied according towhether light that spreads or light that does not spread (i.e.,collimated light) is incident.

Comparing the c-plane and the a-plane against each other with collimatedlight, with a plane rotation angle α of 0 degrees, the polarizationratio value in the c-plane is greater than that in the a-plane.Accordingly, when a collimated light is incident, a light-transmissivemember having an incident surface of the c-plane can have a higherpolarization ratio than a light-transmissive member having an incidentsurface of the a-plane.

According to the experiment result described above, with respect to alight-transmissive member made of sapphire, a consideration as describedbelow can be made as to the case in which the incident surface is aplane parallel to the c-axis and the case in which the incident surfaceis a plane parallel to the c-plane.

Case in which the Incident Surface is a Plane Parallel to the c-Axis

In the incident surface, setting the direction corresponding to theperpendicular direction of the FFP (the major-axis direction of an ovalshape) of laser light to be parallel or perpendicular to the c-axisallows for obtaining a good polarization ratio. Setting the polarizationdirection of laser light becoming incident on the incident surface to beparallel or perpendicular to the c-axis allows for obtaining a goodpolarization ratio is obtained. In other words, setting thes-polarization or the p-polarization to be parallel to the c-axis allowsfor obtaining a good polarization ratio. When light with a smallpolarization ratio value before transmission is transmitted through alight-transmissive member, the polarization ratio value of thetransmitted light is greater than before transmission. As used herein,the expression “light with a small polarization ratio value” refers to,for example, light having polarization ratio in a range of 1 to 50. Evenwhen light propagating along the optical axis is not perpendicularlyincident on the incident surface but is obliquely incident, thepolarization ratio value will not be greatly varied and a stablepolarization ratio is obtained. In other words, with an incident angleof the light propagating along the optical axis relative to the incidentsurface (the plane inclination angle β) in a range of 0 degrees to 90degrees, a stable polarization ratio can be obtained. Accordingly, inthe light emitting device 1, it can be regarded that a good polarizationratio can be obtained when the direction corresponding to theperpendicular direction of the FFP or the polarization direction oflaser light from the semiconductor laser element 20 and the c-axisdirection in the light-transmissive member 60 formed of sapphire areparallel or perpendicular to each other in a top view (or in a bottomview). A polarization ratio of collimated light and a polarization ratioof spreading light do not largely differ from each other.

Case in which the Incident Surface is the c-Plane

When the incident surface is rotated about an axis perpendicularthereto, the polarization ratio does not largely change and a stablepolarization ratio is obtained. By collimating light before the light isincident on the incident surface, a better polarization ratio can beobtained than a polarization ratio when light not collimated is incidenton the incident surface.

As described above, locating a plane parallel to the c-axis of sapphiresuch as the a-plane or the m-plane, or the c-plane, under an appropriatecondition, a good polarization ratio can be obtained. The expression“good polarization ratio” in the present specification refers to apolarization ratio required for an optical device 2.

FIG. 17 is a cross-sectional view showing another embodiment of thelight emitting device. In a light emitting device 1A shown in FIG. 17 ,in a frame part 11A of a base member 10A, a lens member 70A is disposedbelow the light-transmissive member 60. Accordingly, light collimated bythe lens member 70A is incident on the light-transmissive member 60. Insuch a light emitting device 1A, the incident surface of thelight-transmissive member 60 is preferably the c-plane of sapphire. Theincident surface of the light-transmissive member 60 may also be thea-plane.

FIG. 18 is a cross-sectional view showing other embodiment of the lightemitting device. In a light emitting device 1B shown in FIG. 18 , anupper surface of a frame part 11B of a base member 10B is inclined.Accordingly, the light-transmissive member 60 is also disposed to beinclined. Thus, light propagating along the optical axis is notperpendicularly incident on the incident surface of thelight-transmissive member 60. Furthermore, laser light incident on thelight-transmissive member 60 is not collimated, and is transmittedthrough the light-transmissive member 60 while spreading. In such alight emitting device 1B, the incident surface of the light-transmissivemember 60 is preferably the a-plane that is parallel to the c-axis ofsapphire.

Next, a liquid crystal projector will be described below as one exampleof the optical device 2 including the light emitting device according toone embodiment. Examples of the basic configuration of a liquid crystalprojector is described in patent publications such as, for example, JP2018-92112 A, JP 2018-141994 A, and JP 2019-3209 A. As can be seen fromdescription in these publications and other conventional techniques, theliquid crystal projector includes a light source 201, a polarizerelement 202, a liquid crystal panel 203, a projection lens 204 andothers.

Light emitted from the light source 201 is transmitted through thepolarizer element 202 before reaching the liquid crystal panel 203. Forthe polarizer element 202, for example, a beam splitter is used. Withsuch a structure, one polarization component of the light emitted fromthe light source 201 is reflected, and other polarization component istransmitted. That is, the mechanism of the liquid crystal projector isconfigured such that only a particular polarization component isincident on the liquid crystal panel 203. The liquid crystal projectorhaving such a configuration requires light of an good polarizationratio. For example, the light source 201 is demanded of emitting lighthaving polarization ratio value of 100 or more.

Accordingly, as shown in FIG. 19 , the liquid crystal projector in whichthe light emitting device according to one embodiment is employed as thelight source 201 can efficiently cause light of a particularpolarization component to be incident on the liquid crystal panel 203.More specifically, the liquid crystal projector includes the lightemitting device 1. The liquid crystal projector further includes thepolarizer element 202 on which light emitted from the light emittingdevice 1 is incident. The liquid crystal projector further includes theliquid crystal panel 203 on which light emitted from the light emittingdevice 1 and transmitted through the polarizer element 202 is incident.The liquid crystal projector further includes the projection lens 204projecting a projection image created according to light emitted fromthe light emitting device 1. The liquid crystal projector may furtherinclude other components.

While certain embodiments of a light emitting device and an opticaldevice have been described above, the light emitting device and theoptical device according to the present invention are not limited tothose in the embodiments described above. That is, the present inventioncan be implemented without limitation of the outer shape orconfiguration of the light emitting device and the optical device tothose in the embodiments described above. The present invention is alsoapplicable to a device not including all elements illustrated in theembodiments described above. For example, when the claims do not recitesome elements of the light emitting device in the embodiments describedabove, a light emitting device in which replacement, omission,modification, change in material, or the like of such elements is madeby a person skilled in the art is within the scope of the claims. Thus,design flexibility of such elements is allowed for application of thepresent invention.

The light emitting device according to the embodiments is applicable toa light source for a projector, a vehicle headlight, illumination, adisplay device, and the like.

What is claimed is:
 1. A light emitting device comprising: at least onesemiconductor laser element; a base member on which the at least onesemiconductor laser element is disposed; a light-transmissive memberincluding: an upper surface, a lower surface, and a light-transmissiveregion through which laser light emitted from the at least onesemiconductor laser element is transmitted from the lower surface to theupper surface; and a lens member through which the laser light emittedfrom the at least one semiconductor laser element, the lens member beingfixed to the base member or the light-transmissive member, wherein: atleast the light-transmissive region is made of sapphire, and thelight-transmissive member includes an incident surface on which thelaser light is incident, the incident surface being an a-plane of thesapphire.
 2. The light emitting device according to claim 1, wherein:the light-transmissive member is oriented such that a polarizationdirection of the laser light incident on the incident surface isparallel or perpendicular to a c-axis of the sapphire in a top view. 3.The light emitting device according to claim 1, wherein: the at leastone semiconductor laser element comprises a plurality of thesemiconductor laser elements, and the incident surface of thelight-transmissive member is oriented so that a polarization directionof beams of the laser light emitted from the plurality of semiconductorlaser elements is parallel to or perpendicular to the c-axis of thesapphire in a top view.
 4. The light emitting device according to claim1, wherein the at least one semiconductor laser element includes aTE-mode semiconductor laser element and a TM-mode semiconductor laserelement.
 5. The light emitting device according to claim 1, wherein: theat least one semiconductor laser element includes a first semiconductorlaser element and a second semiconductor laser element, and apropagation direction of light emitted from the first semiconductorlaser element and propagating along the optical axis of the firstsemiconductor laser element and a propagation direction of light emittedfrom second semiconductor laser element and propagating along theoptical axis of the second semiconductor laser element are differentfrom each other by 90 degrees in a top view.
 6. The light emittingdevice according to claim 1, wherein: the laser light emitted from thelight-transmissive member is transmitted through the lens member.
 7. Thelight emitting device according to claim 1, wherein: a thickness of thelight-transmissive member between the incident surface on which thelaser light is incident and an emission surface from which the laserlight is emitted is in a range of 0.3 mm to 1.0 mm.
 8. The lightemitting device according to claim 1, further comprising: at least onelight-reflective member disposed on the base member and including alight-reflective surface configured to reflect the light emitted fromthe at least one semiconductor laser element, wherein: the laser lightreflected by the at least one light-reflective member is incident on theincident surface.
 9. A light emitting device comprising: at least onesemiconductor laser element; a base member on which the at least onesemiconductor laser element is disposed; a light-transmissive memberincluding: an upper surface, a lower surface, and a light-transmissiveregion through which laser light emitted from the at least onesemiconductor laser element is transmitted from the lower surface to theupper surface; and a lens member through which the laser light emittedfrom the at least one semiconductor laser element, the lens member beingfixed to the base member or the light-transmissive member, wherein: atleast the light-transmissive region is made of sapphire, and thelight-transmissive member includes an incident surface on which thelaser light is incident, the incident surface being an m-plane of thesapphire.
 10. The light emitting device according to claim 9, wherein:the light-transmissive member is oriented such that a polarizationdirection of the laser light incident on the incident surface isparallel or perpendicular to a c-axis of the sapphire in a top view. 11.The light emitting device according to claim 9, wherein: the at leastone semiconductor laser element comprises a plurality of thesemiconductor laser elements, the incident surface of thelight-transmissive member is oriented so that a polarization directionof beams of the laser light emitted from the plurality of semiconductorlaser elements is parallel to or perpendicular to the c-axis of thesapphire in a top view.
 12. The light emitting device according to claim9, wherein: the at least one semiconductor laser element includes aTE-mode semiconductor laser element and a TM-mode semiconductor laserelement.
 13. The light emitting device according to claim 9, wherein:the at least one semiconductor laser element includes a firstsemiconductor laser element and a second semiconductor laser element,and a propagation direction of light emitted from the firstsemiconductor laser element and propagating along the optical axis ofthe first semiconductor laser element and a propagation direction oflight emitted from second semiconductor laser element and propagatingalong the optical axis of the second semiconductor laser element aredifferent from each other by 90 degrees in a top view.
 14. The lightemitting device according to claim 9, wherein: the laser light emittedfrom the light-transmissive member is transmitted through the lensmember.
 15. The light emitting device according to claim 9, wherein: athickness of the light-transmissive member between the incident surfaceon which the laser light is incident and an emission surface from whichthe laser light is emitted is in a range of 0.3 mm to 1.0 mm.
 16. Thelight emitting device according to claim 9, further comprising: at leastone light-reflective member disposed on the base member and including alight-reflective surface configured to reflect the light emitted fromthe at least one semiconductor laser element, wherein: the laser lightreflected by the at least one light-reflective member is incident on theincident surface.